// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_CHILD_WORKER_THREAD_REGISTRY_H_
#define CONTENT_CHILD_WORKER_THREAD_REGISTRY_H_

#include <map>

#include "base/callback_forward.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "base/threading/platform_thread.h"
#include "content/common/content_export.h"
#include "content/public/child/worker_thread.h"

namespace base {
class TaskRunner;
}

namespace content {

class CONTENT_EXPORT WorkerThreadRegistry {
public:
    WorkerThreadRegistry();

    int PostTaskToAllThreads(const base::Closure& task);
    static WorkerThreadRegistry* Instance();

    void DidStartCurrentWorkerThread();
    void WillStopCurrentWorkerThread();

    // Always returns a non-null task runner regardless of whether the
    // corresponding worker thread is gone or not. If the thread is already gone
    // the tasks posted onto the task runner will be silently discarded.
    base::TaskRunner* GetTaskRunnerFor(int worker_id);

private:
    friend class WorkerThread;
    friend class WorkerThreadRegistryTest;

    bool PostTask(int id, const base::Closure& task);

    using IDToTaskRunnerMap = std::map<base::PlatformThreadId, base::TaskRunner*>;

    ~WorkerThreadRegistry();

    // It is possible for an IPC message to arrive for a worker thread that has
    // already gone away. In such cases, it is still necessary to provide a
    // task-runner for that particular thread, because otherwise the message will
    // end up being handled as per usual in the main-thread, causing incorrect
    // results. |task_runner_for_dead_worker_| is used to handle such messages,
    // which silently discards all the tasks it receives.
    scoped_refptr<base::TaskRunner> task_runner_for_dead_worker_;

    IDToTaskRunnerMap task_runner_map_;
    base::Lock task_runner_map_lock_;
};

} // namespace content

#endif // CONTENT_CHILD_WORKER_THREAD_REGISTRY_H_
